An O/T but interesting Topic

[Peter Ford]

Thanks for you replies David, Johan and Ted.

First I have a correction.  The combined RF power output into the mast is 
currently 250 KW.

At the petrol pump we are advised not to use mobile communications devices - 
This is UHF at less than 2 Watts.

An Induction cooktop boils water very quickly - EVLF at about 1 KW - but 
minimal spacing between the pot and the induction coil.

MF AM Radio is between these.  We have 250,000 KW at 0.5 Km from the metal 
film cans/shelves.  So will there be any heating effect and is there a risk 
of RF arcing?

Peter




When I was at college, I earned extra cash by babysitting the KDNT AM 
transmitter site from pre-sunrise sign-on till after sunrise when I changed 
antenna patterns and transmitter power. I had my First Phone and could use 
the cash, so I was game.

There was so much RF in the transmitter shack that I could not sit in the 
folding metal chair less my lower extremities would start burning.

In regard to nitrate, I don't think there would be enough energy in the RF 
field to cause an issue unless the material was right up next to the 
antenna. RF experts can chime in on the ratio of RF energy verses distance 
from the radiation source (it drops off quite rapidly).

Regards,

David Crosthwait


On Mar 1, 2016, at 1:03 PM, Johan Glas via QuadList wrote:

Nitrate is very dangerous burning, but try to start the fire, not easy. The 
danger here pointed out seems minor to zero to me.

Johan Glas, the Netherlands


Film cans as RF powered heaters.  Hmmm.

There's at least one member of the group that might have a thought. I've 
forwarded this to him and he may reply either directly or through the group.

Perhaps someone should be going into more than one of the vaults and doing 
some measurements with appropriate equipment?

If the building is concrete and made with any kind of wire mesh in the 
concrete, is it possibly acting as a Faraday cage?

Is there any plan to rebuild the taller antenna using the same antenna base, 
Et Cetera?

Ted


This is off topic, but members of the group may be able to help with advice 
as many of you have backgrounds in Radio and Television Broadcasting.

A Film and Tape Audio-Visual Archive (where I have previously carried out 
quad restoration work using an AVR1 - the connection?) is not permitted to 
store Videotape/Safety Film and Nitro-Cellulose (Nitrate) film in the same 
building.  Except for very small quantities undergoing restoration the bulk 
of the Nitrate Film collection had to be stored in disused ammunition 
bunkers in an isolated spot in the countryside.

About two years ago this Archive and the Government Archive combined their 
Nitrate Film Collections in a brand new purpose built climate controlled 
secure vault in a secret location.  Very commendable - but I have found the 
location and I see there may be a big problem.

About 40 Km from the city centre is an AM Radio Transmission site.  There 
are five transmitters with a combined output of about 150 KW.  They had two 
masts one 220 meters high and the other 137 meters.  However  recently the 
220 meter mast was discovered to have a corrosion problem and was dropped 
with explosives.  It was this activity that drew my attention to the site. 
To my surprise I  found the new Nitrate Film vault.  It had been built here 
over the top of the ground radials for the 220 meter mast and 0.5 km from 
the 137 meter mast.

Nitrate Film is extremely flammable....it has almost the same composition as 
Nitro-Glycerine a very hot burning explosive (5000 degrees C).  Having a 
large quantity of this stuff located in a very strong RF electromagnetic 
field is asking for trouble.  The films are in individual metal containers 
stacked 8 high on painted metal shelving.  My theory is each stack of 8 cans 
will be acting as an aerial and there will be a large RF potential 
difference between the bottom of the stacks and the shelving.  This is an 
ignition or detonation source only being suppressed by a thin layer of 
paint.  Because the transmitters run 24/7 if an arc starts it will not stop.

I spoke to the local council about the danger.  They assured me the vault 
has a 4 hour fire rating therefore complied with regulations.

Anyone agree with me this is a very dangerous situation?